-•• Vi-, t! Response of the Coastline to Climate change Specific Report for the RESPONSE Project LIFE- Environment programm: Evolution of coastal risk (erosion and marine flooding) for the Aquitaine yfr, v and Languedoç-Roussillon pilot regions BRGM/RP-54718-FR • ',v- September, 2006 Response 3 5000 00055613 3 brgGeoscienceformj sustainable Earth Response of the Coastline to Climate change Specific Report for the RESPONSE Project LIFE- Environment programm: Evolution of coastal risk (erosion and marine flooding) for the Aquitaine and Languedoc-Roussillon pilot regions Final report BRGM/RP-54718-FR September, 2006 Study conducted as part of research projects 2003-2006 RISCOTE18/PC3 C. Vinchon, D. Idier, M. Garcin, Y. Balouin, C. Mallet, S. Aubié, L. Closset With the collaboration of C. Oliveros, R. Pedreros and N. Le nôtre Checked by: Approved by: Original signed by: Original signed by: Name: C. OLIVEROS Name: H. MODARESSI Date: 30/10/2006 Date: 30/10/2006 Signature: .Signature: The quality management system of BRGM is certified according to AFAQ ISO 9001:2000. BJR G 2 1 NOV. 2006 Geosciencefora sustainable Earth BIBLIOTHEQUE brgm Keywords: Climate change, Coastal risk, Coastal erosion, Marine flooding, Aquitaine, Languedoc-Roussillon, Change in hazards, Assets at risk. Change in risk, Hotspots. In bibliography, this report should be cited as follows: Vinchon C, Idler D., Garcin M., Balouin Y., Mallet C, Aubié S., Closset L. with the collaboration of Oliveros C, Pedreros R. and Lenôtre N. (2006) - Response of the Coastline to Climate Change. Specific Report for the RESPONSE Project LIFE-Environment programm: Evolution of coastal risk (erosion and marine flooding) on the Aquitaine and Languedoc- Roussillon pilot regions. Final report. BRGM/RP-54718-FR. 153 p., 27 figs, 19 tables, 9 app., 1 CD-ROM. © BRGM, 2006. No part of this document may be reproduced without the prior permission from BRGM. Response of the coastline to climate change Synopsis As stated in the project specification document, the RESPONSE project aims "to develop sustainable strategies for management natural hazards in coastal areas taking account of the impact of climate change". The RESPONSE project received funding from the European LIFE-Environment program. BRGM's participation in the project was ensured jointly by European funding and a research endowment to BRGM from the Ministry for Research. The purpose of this report is to define BRGM's role in the RESPONSE project and to explain the results obtained for the two French pilot regions, Aquitaine and Languedoc- Roussillon. This document will be appended to the final report submitted by the RESPONSE project's coordinator. It also aims to be comprehensive so as to further dissemination of the methodology. The first chapter describes the mapping methodology, starting with the existing data on through to the risk map, underlining adaptations that were made of the method initially proposed, that was based on experimental studies conducted for south-eastern counties in England (Hosking ei a/., 2002; Cooper ei al., 2002). For each step of the mapping process, an analysis of the results for the considered regions is provided. The first phase was to map "coastal behaviour systems" that are thought to respond in a coherent manner to the impact of climate change. This was conducted using existing data on geomorphology, coastal processes, historical hazard events as well as existing defence works. The result of this mapping process underlines an existing vulnerability of the coastline in both regions with respect to erosion and marine flooding on most of the low-lying sandy Languedoc coast, and also on parts of the Aquitaine sandy coast where the dune system is cut by coastal river outlets. The efficiency of existing defences on these coastlines is questionable in some places. The cliff-lined coast of Aquitaine, made of weathered sedimentary rocks, is subject to ground movement hazard, while the hard Cambrian rocks on the Roussillon coast proved to be more stable. The second phase was to propose a regional adaptation of the modelling of global climate change impacts. To answer to the end-users' demands and to obtain a wider scope of the likely future critical conditions, the most pessimistic scenario is chosen for the potential rise in sea level, which is added to the maximum present-day sea level at high tide and to the known storm surge specific to each considered region. The third phase was to evaluate the change in the erosion and marine flooding hazards, judged by a panel of experts called on to assess the impacts of the regional climate change scenarios upon the coastal systems described above. Both regions exhibit an increased level of the hazards considered, to degrees ranging between significant and drastic. However, due to the sedimentary stock present in dune BRGM/RP-54718-FR - Final report Response of the coastline to climate change systems, the sandy Aquitaine coast displays a better capacity for adaptation to change than the Languedoc-Roussillon lidos. Existing hazards persist and new segments would join the list of those endangered, such as small pocket beaches, where little sedimentary stock is found. The fourth phase was to evaluate which assets would be placed at risk by an increase in the coastal erosion and marine flooding hazard. In Aquitaine, mainly urbanized and tourist assets concentrated around the outlets of coastal rivers on the sandy coast and on the cliff-lined coast of Pays Basque will be endangered, in addition to industrial assets that in spots could be flooded in the hinterland. Due to widespread development of the Languedoc-Roussillon coastline, urban, tourist, industrial and agricultural assets would be placed at risk, more specifically those inland from the systems of lidos. Throughout this procedure, "hotspots" defined as areas requiring highest priority for attention, were identified, first as existing and studied hotspots (SMNLR, 2003),then as spots or streches of coast where the hazards are likely to increase drastically, and lastely as spots (or streches of coast lines) where drastically increasing hazrds would put assets as risk (this last step answering the RESPONSE methodology definition "as sectors classified at higher risk on the basis of present or future hazard maps". Individual statement files of some of those hotspots is given in Appendix 4. The second chapter presents the estimates obtained for the present and future costs of managing coastal risks, although this task (Task 2) has proven difficult to accomplish according to the terms of the project submitted to LIFE-Environment. Accompanying this report are appendixes relative to the report content, and also ones presenting complementary information gathered during that project such as the status of research on climate change and coastal environments in France, and the assessment of dissemination efforts for the RESPONSE project. BRGM/RP-54718-FR - Final report Response of the coastline to climate change Contents 1. Presentation of the RESPONSE Project .11 1.1. CONTEXT 11 1.1.1. The coastal zone at the beginning of the 21st century 11 1.1.2. Global warming 11 1.1.3. The impact of global warming on the coastal zone 12 1 .2. THE RESPONSE PROJECT: OBJECTIVE AND APPROACH 12 1.2.1. The objective 12 1.2.2. Project organization 13 1.2.3. The choice of French pilot regions 16 1.3. OBJECT OF THIS REPORT 21 2. The mapping process 23 2.1. PRESENTATION OF THE METHOD 23 2.2. DATA AND METADATA SOURCES 24 2.2.1. Metadata 24 2.2.2. Data 25 2.2.3. Data ownership 25 2.3. COMPILING AND MAPPING EXISTING DATA 25 2.3.1. Geomorphology and coastal processes maps (Maps 1a and 1b) 25 2.3.2. Map of works and defence means against the sea (Map 2, Appendix 4 - CD-ROM) 29 2.3.3. Map of historical and present-day hazards (Map 3, Appendix 4 - CD-ROM) 30 2.4. PHASE 1 : DEFINING GEOMORPHOLOGICAL COASTAL BEHAVIOUR SYSTEMS AFFECTED BY CLIMATE CHANGE 31 2.4.1 . Defining coastal behaviour systems by combining geomorpho-logical elements 31 2.4.2. Validation 33 2.4.3. The aggregation of the coastal behaviour systems 33 2.4.4. Present-day marine flooding hazard 34 2.4.5. Summary of results: the main characteristics of the two pilot regions 34 2.4.6. A preliminary identification of present-day hotspots in the French pilot regions 36 BRGM/RP-54718-FR - Final report Response of the coastline to climate change 2.5. PHASE 2: BUILDING REGIONAL CLIMATE CHANGE SCENARIOS 40 2.5.1. Hypotheses and models from IPCC 2001 40 2.5.2. Comparisons between models in order to define regional scenarios 43 2.5.3. The choice of a climate scenario for the two French pilot regions 48 2.6. PHASE 3: EVALUATING AND MAPPING EVOLUTION OF COASTAL HAZARD 49 2.6.1. Method 49 2.6.2. Grading hazard change 50 2.6.3. Mapping 51 2.6.4. Analysis of results 52 2.7. PHASE 4: EVALUATION OF THE ASSETS PLACED AT RISK DUE TO HAZARD CHANGE 63 2.7.1. Method 63 2.7.2. Mapping assets 64 2.7.3. Mapping the change in coastal risk 65 2.7.4. Analysis of results 66 3. Assessing the present and future costs of coastal risk management 79 3.1. A WARNING REMARK 79 3.2. PRESENT-DAY COASTAL RISK MANAGEMENT COSTS 79 3.2.1. Data sources 79 3.2.2. Results 80 3.3. THE EVOLUTION OF RISK MANAGEMENT COSTS OVER THE 21 ST CENTURY 85 3.3.1. Hypothesis on the choice of strategies 85 3.3.2. Application to French pilot regions 86 3.4. CONCLUSIONS ON EVALUATING THE COSTS OF COASTAL RISKS AND COASTAL RISK CHANGES 87 4.